Method of recovering film scrap



Patented Jan. 4, 1944 METHOD OF RECOVERING FILM SCRAP Alfred D. Slack,Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N. Y., acorporation of New Jersey No Drawing. Application January 23, 1943,Serial No. 473,429

6 Claims.

This invention relates to the reclamation of cellulose ester sheetingwhich contains a thin layer of cellulose nitrate thereon, such as metwith in photographic film scrap.

In the manufacture of photographic film in which a lower fatty acidester of cellulose, such as cellulose acetate, cellulose acetatepropionate, or cellulose acetate butyrate, is employed as the film base,it is ordinarily necessary to employ a subbing layer to cause thephotosensitive gelatin emulsion to adhere thereto. One of the mostcommonly employed subbing layers is a thin layer of cellulose nitrateand/or gelatin or other watersoluble material. In making photographicfilm the production of more or less waste is often unavoidable. Toprocess this waste film for salvage purposes requires the removal of thenitrate subbing layer from the film base. Also, used film which is nolonger of value and has been discarded, in order to be employed for someuseful purpose must be treated to separate the gelatin and the nitratesubbing layers therefrom.

One object of my invention is to provide a method of removing thenitrate subbing layer from sheeting of an organic acid ester ofcellulose without deleteriously affecting the organic acid ester ofcellulose which will be referred to herein, for purposes ofillustration, as cellulose acetate. Other objects of my invention willappear herein.

My invention involves the treatment of the scrap material at an elevatedtemperature with a dilute solution of an amine having trivalent nitrogenuntil the thin nitrate layer thereon is completely removed therefromwithout contamination from the presence of any cellulose nitrate,

The cellulose ester material may, for instance, be treated with anaqueous solution of an amine of concentration at 145 F. for twenty hourstime. Although concentrations of not more than 1% have been found tosatisfactorily remove the nitrate, higher concentrations can be used(limiting the concentration being only for economical reasons) but withno better results and, therefore, concentrations of not over 1%, such asto are most desirable. Also, the time of treatment is not fixed butdepends to a great extent upon the temperature employed in treating thecellulose ester material. For example, temperatures of 140-160, and aprocessing time of fifteen-twenty hours may be required. With highertemperatures shorter times are satisfactory. For instance, with atemperature of 180 F. the processing time may be reduced to from one tothree hours. With temperatures above 180 F. a time of not more than onehour is ordinarily sufficient, the use of pressure bringing the timedown still more. The time of treatmentshould be that which is suflicientto completely remove the subbing layer from the cellulose estersheeting, and the time will be governed by the accomplishment of thispurpose. With a lower temperature such as much longer times arenecessary than given, hence this is about the minimum temperature whichone would care to use. In cases where films have backing dyes, such ascarried by a backing layer or applied as a coating on the back of thefilm, it may be desirable to continue the treatment for a longer time todiminish or completely remove the dye, which is present, therefrom. Incases of film in which the. dyes are also present in the emulsionlayers, such as with Kodachrome or other colored films, it is desirablethat the treatment for removal of the gelatin from the film containssome adsorbing material, such as activated carbon, to take up the colorduring that treatment.

The amines which may be employed for treating scrap material inaccordance with my invention are of various types, all ofwhich have beenfound to be effective, although in some cases, some of these amines formcolored compounds which may stain the sheeting proper, and consequentlysome compounds of this type are more desirable than others. The amineswhich are useful in my invention may be conveniently divided into thefollowing classes:

1. Alkylolaminesamong the amines of this type which have been foundsatisfactory'for this purpose are ethanolamine, diethanolamine,triethanolamine, monoisopropanolamine, and butyl amino ethanol.

2. Alkylamines-the lower alkyl amines, such as methyland ethylamines areefiective, but because of their low boiling point and high volatilitythey are less well adapted to this process than the higher alkylaminessuch as dibutylamine, diamylamine, octylamine, and the like,

which are not driven off so easily under elevatedv temperatureconditions. Any of these amines which are not sufiiciently soluble inwater may be combined with acids which facilitate water solutions, suchas lactic acid or acetic acid.

3. Arylamines benzylamine and benzyldiethanolamine have been found to bevery efiective for the purposes of my invention. With the arylamines,however, it is desirable that too high a temperature or too high aconcentration of the amine be avoided, particularly with compounds suchas aniline, p-toluidine, dimethyl aniline, or the like, due to theircolor-forming tendencies.

l. Cyclic tertiary aminesamines of this nature have been found to bequite suitable for use in accordance with my invention. Ethyl morpholineand methyl morpholine are representative of the types of compounds whichare satisfactory for removing the nitrate subbing layer from celluloseacetate base films.

5-. Heterocyclic compoundssome of the amines under this designation areless active than other types of 1 compounds. For instance, pyridineexhibits a slow action and, a so, is not preferred for'use in thisconnection because of its volatility. Quinoline also requires a longerprocessing time than is necessary with other amines. Compounds, however,of the nature of methylated pyridines, such as collidine or hexylpyridine, have been found to be quite effective and avoid thedisadvantages of pyridine and quinoline.

As has been pointed out, it is desirable that the amine which isemployed for reclaiming cellulose esters in accordance with my inventionhave a rather high boiling point and low volatility as obviously, underthe circumstances of use encountered in my invention, highly volatilematerials introduce problems which may be avoided by the properselection of the amines to be employed for this purpose.

As my invention is adapted primarily to the recovery of photographicfilm scrap, it will be particularly described with reference thereto.The film scrap is preferably first chopped up into small particles andsubjected to the action of water, preferably having a temperature of90-120 F., either with or without a digestive enzyme, such aspancreatin, to remove the gelatin emulsion therefrom. If colored film orsuper sensitive film is being processed it is also desirable toincorporate in the warm water used to remove the gelatin emulsion anadsorbent such as activated carbon, silica gel, alumina, or absorbentearth in the mass so that the dye, particularly if of a Water-solubletype, is adsorbed thereby rather than being allowed to bleed into thecel lulose ester material. This treatment is carried out for some timeat a temperature between 90 F. and 120 F. until the gelatin iscompletely removed from the cellulose ester sheet. After removing thegelatin the material is washed and then treated with the hot aqueoussolution of an amine at an elevated temperature for a sufficient time toremove the nitrate subbing layer from the film.- Ordinarily theproportion of scrap to liquid is 1:20, or in other words, sulficient ofthe solution is employed to completely immerse the material beingtreated.

The following examples illustrate my invention:

- Example I 50 parts of scrap film having a cellulose acetate base andcontaining a cellulose nitrate subbing layer, such as is described andclaimed in U. S. patent No. 2,014,547 of G. S. Babcock, were immersed ina mixture of 1000 parts of water and 2.5 parts of 2:4:6 trimethylpyridine. The mass was maintained at a temperature of 180 F. for aperiod of about three hours. The material was then washed and dried andwas found to be suitable for solution in solvents for cellulose acetatein which cellulose nitrate does not dissolve in appreciable amounts. Theresulting solutions are practically colorless (that is, no

more color is present than is visible in the original solution fromwhich the base was first formed) and upon spreading the solution or dopeupon a film-forming surface there is obtained transparent sheeting freefrom grain and haze.

Example II hours. The material was washed and dried and was found to besuitable for solution in solvents for cellulose acetate in whichcellulose nitrate does not dissolve in appreciable amounts. Theresulting solutions are practically colorless (that is, no more color ispresent than is visible in the original solution from which the base wasfirst formed) and upon spreading the solution or dope upon afilm-forming surface there is obtained transparent sheeting free fromgrain and haze.

E mample III The details of Example I were followed except that 2 partsof stearyl dimethylamine were employed instead of trimethylpyridine.Similar results were obtained.

I claim:

1. A process of recovering a lower fatty acid ester of cellulose fromsheeting comprising a base of the cellulose ester and an overcoating ofcellulose nitrate thereon, which comprises subjecting the sheeting tothe action of a dilute aqueous solution of an amine selected from thegroup consisting of alkylolamines, alkylamines, arylamines and cyclictertiary amines at a temperature of at least F. for a sufiicient time tosubstantially completely remove the cellulose nitrate therefrom.

2. A process of recovering a lower fatty acid ester of cellulose fromsheeting comprising a base of the cellulose ester and an overcoating ofcellulose nitrate thereon, which comprises subjecting the sheeting tothe action of water containing -1% of an amine selected from the groupconsisting of alkylolamines, aikylamines, arylamines and cyclic tertiaryamines at a temperature of at least 125 F. for a suiiicient time tosubstantially completely remove the cellulose nitrate therefrom.

3. A process of recovering a lower fatty acid ester of cellulose fromsheeting comprising a base of the cellulose ester and an overcoating ofcellulose nitrate thereon, which comprises subjecting the sheeting tothe action of a dilute aqueous solution of an amine selected from thegroup consisting of alkylolamines, alkylarnines, arylamines and cyclictertiary amines, at 180-212 F. for one hour.

4:. A process of recovering, a lowerfatty acid ester of cellulose fromsheeting comprising a base of the cellulose ester and an overcoating ofcellulose nitrate thereon, which comprises subjecting the sheeting tothe action of a dilute aqueous solution of an alkylolamine at atemperature of at least F. for a sufficient time to substantiallycompletely remove the cellulose nitrate therefrom.

5. A process of recovering a lower fatty acid ester of cellulose fromsheeting comprising a base of the cellulose ester and an overcoating ofcellulose nitrate thereon, which comprises subject ing the sheeting tothe reaction of water containing %l% of an alkylolamine at a temperatureof -212" F. for approximately one hour.

6. A process of recovering a lower fatty acid ester of cellulose fromsheeting comprising a base of the cellulose ester and an overcoating ofcellulose nitrate thereon, which comprises subjecting the sheeting tothe reaction of water containing /4-1% of a dimethylethanolamine at atemperature of 130-212" F. for approximately one I hour.

ALFRED D. SLACK.

